IPS monitors tend to be several hundred dollars more than TN panels of comparable size. The trade-off here is much better viewing angles and color representation and in the case of the U2711, a much higher pixel density at a native resolution of 2560 x 1440 (109 ppi vs. 82 ppi for standard 1920 x 1080 27" displays).

A 6 ms response is more than sufficient for gaming. Anything under 15 ms is acceptable, which is where IPS monitors top out at in terms of black to white transitions (ISO standard).

Just for clarification, the fastest response time possible currently are GTG transitions. This is due to the advent of Response Time Compensation/Overdrive, which have allow GTG transitions to surpass ISO transition times.

ISO transition times have hit a wall in recent years, with TN panels topping out at 5 ms, IPS panels at 15 ms and MVA panels at around 12 ms.